This invention relates to forming rolls used in metal forming and in particular to the supporting mechanism for the bearing arrangement used to rotatably mount the large, heavy rolls, commonly called back-up and work rolls.
It is well known to mount a main roll of a rolling mill in top and bottom chalks in which are mounted suitable bearings. At the outboard and inboard end of the bearings are provided collars. In one known arrangement, the outboard collar has a bearing retainer extending around its circumference, which retainer is held in place by bolts threaded into the chalks. A thrust collar bears against the axial outer face of the outboard collar. Extending about the inboard collar is a seal ring that is mounted by bolts to the chalks.
It is also known to use plane bearings (usually babbit) to rotatably support the large rolls in a rolling mill. These bearings which use a large quantity of oil in order to operate can be used in conjunction with tapered roller bearings mounted axially outwardly from the plane bearing. The inner bearing support is held in place by the use of a split ring that is threaded on the outside and that is mounted in a circumferential recess formed in the roll end. The split ring is held in place by a complete exterior ring having internal threads and it is this exterior ring that actually bears against the side of the inner bearing support. The end of the roll and its exterior ring are covered by a protective cap. This arrangement for mounting bearings on the end of the rolls has several inherent disadvantages including the fact that the threads on the rings can be easily damaged and there is a possibility of injury to workmen because of the known method for tightening the threaded exterior ring (this method employs a pin and cable). The known methods for mounting the bearings is time consuming and it will be appreciated that it is important to reduce the downtime for these rolling mills as much as possible in view of the cost of such mills.
The use of a device known as "a hydraulic nut" is known in rolling mill construction, particularly in the construction of prestressed roll stands. The device can consist of ring-shaped members, namely a cylinder and a piston. In one known arrangement in a rolling mill, one of these members is directly connected with a tie rod by means of a clamp nut and is displaced with the expansion of the tie rod under hydraulic stressing, the other member resting against a support. For example a hydraulic stressing device as shown in U.S. Pat. No. 3,588,044 issued Jun. 28, 1971 to E. G. Reichrath and O. K. Buchheit. The device taught in this patent specification consists of a ring cylinder and a ring piston surrounding a tie rod. The piston is pressed downwardly by means of screw bolts and is connected directly through a divided ring with the end of the tie rod by engaging beneath a protruberance at the end of the tie rod. Fluid pressure is used to actually expand the tie rod in order to clamp the components together with a selected clamping force.
U.S. Pat. No. 4,581,911 issued Apr. 15, 1986 to Y. Shinomoto describes a cantilever-type rolling mill having a pair of roll shafts rotatably supported in a roll housing. The rolling mill includes a tension member provided axially through the center of the roll shaft and having the outer end thereof projecting out of the roll shaft. There is a roll compressing tool detachably engageable with the projecting end of the tension member, which tool incorporates a hydraulic piston-cylinder. The tool has a nut member threadably fitted on the outer periphery of the cylinder. An extraction ring interlocks the roll unit with the tool. An oil pressure passage in the cylinder communicates with an annular groove located at the inner end of the piston. In order to mount the roll unit, this unit is mounted on the tool by the use of the extraction ring and then the unit and the tool are fitted onto the roll shaft using a jig. Clearly this known hydraulic piston-cylinder mechanism is not used to hold any bearing arrangement for the end of the roll in place.
The hydraulic piston-cylinder mechanism or nut is single acting, that is, it cannot be pressurized hydraulically in more than one direction. It is pressurized during the mounting or assembly operation only and after this operation is completed, the pressure in this hydraulic nut is removed.
Although it is believed by the applicants that the use of hydraulic nuts to mount the bearing arrangement for a roll in a rolling mill has been proposed in the past, such proposals have not met with widespread commercial success. Some of these proposals have been in practice unworkable and because of the high cost of rolling mills in general, this industry has been reluctant to accept and adopt new construction techniques for these mills, at least until a new construction has proven itself as being a definite improvement.
A drawing produced by the Timken Company shows a hydraulic nut arrangement for holding in place a tapered four roll T.O.O. roller bearing mounted on the reduced end of a work roll. The hydraulic nut is formed by two ring-shaped inner and outer sections. The outer ring section has a L-shaped cross-section and it is this section that bears against a further ring member whose inner end bears against the inner bearing support. Two ring-shaped seals appear to be provided between the contacting surfaces of the inner and outer ring sections that form the hydraulic nut. Another ring member is mounted on the outer end of the roll to bear against the outer end of the inner ring section and hold the section against axially outward movement.
It is an object of the present invention to provide a hydraulic fastener for mounting one end of a roll in a rolling mill stand, said fastener being reliable and relatively easy to construct and to use.
It is a further object of the invention to provide a hydraulic fastener which can be used not only to mount one end of a roll in a rolling mill stand but which is kept under pressure during operation of the rolling mill.